Technically Speaking
Demand at 320 has held going back to February of 2015.
If that level fails to hold, the next level of support is at 260, 18% to the downside.
Risk
What is the probability of a permanent loss of capital?
How much of my capital am I going to put at risk? 1%, 3%? You have to make this decision. Remember, deep drawdowns are hard to come out...